伊犁蒙其古尔铀矿床含矿层砂岩中黄铁矿形成机制及对铀成矿的指示意义  

Mineralogical and isotopes evidence for origin of pyrite: Implication for formation mechanism of pyrite and its relationship with uranium mineralization in Mengqigu’er uranium deposit, Yili Basin

作　　者：丁波[1] 刘红旭[1] 张宾 李平[1] 蒋宏[2] 张虎军[2] 谢希良 郭春杰 DING Bo;LIU HongXu;ZHANG Bin;LI Ping;JIANG Hong;ZHANG HuJun;XIE XiLiang;GUO ChunJie(CNNC Key Laboratory of Uranium Resources Exploration and Evaluation Techniques,Beijing Research Institute of Uranium Geology,Beijing 100029,China;Geological Party No.216,CNNC,Urumqi 830011,Xinjiang,China;Xinjiang Tianshan Uranium Co.,Ltd.,CNNC,Yining 835000,Xinjiang,China)

机构地区：[1]中核集团铀资源勘查与评价重点实验室,核工业北京地质研究院,北京100029 [2]核工业二一六大队,新疆乌鲁木齐830011 [3]新疆中核天山铀业有限公司,新疆伊宁835000

出　　处：《矿床地质》2019年第6期1379-1391,共13页Mineral Deposits

基　　金：国家科技部973计划项目（编号:2015CB453004）;中核集团集中研发项目“伊犁盆地南缘东段砂岩型铀矿定位预测与靶区优选（编号：地LTD1612-4）;国家预先研究项目（编号：3210402）联合资助

摘　　要：蒙其古尔铀矿床为伊犁盆地南缘大型层间氧化带砂岩型铀矿床,为查明该矿床含矿层中黄铁矿成因及其形成机制,探讨微生物参与铀成矿过程。文章对含矿层砂岩中黄铁矿与铀矿物矿物学特征、黄铁矿S同位素与碳酸盐胶结物的C-O同位素开展细致研究。研究表明:①蒙其古尔铀矿床中铀主要以铀矿物与吸附铀形式存在,吸附铀主要为有机质吸附铀,铀矿物以沥青铀矿为主,多与黄铁矿、炭屑共生;②蒙其古尔铀矿床含矿层砂岩中黄铁矿主要以自形晶、草莓状和不规则状集合体产出,多与沥青铀矿、碳酸盐胶结物共生,其中黄铁矿S同位素(δ34SV-CDT=-68.4‰~22.1‰)与碳酸盐胶结物的C-O同位素(δ13CV-PDB=-10.2‰^-7.4‰,δ18OV-PDB=-9.6‰^-5.8‰)分析表明黄铁矿具有细菌硫酸盐还原(BSR)与有机物热解2种成因,并探讨了这2种不同成因黄铁矿的形成机制。③结合前人研究成果,认为硫酸盐还原菌(SRB)参与蒙其古尔铀矿床铀成矿过程,以间接还原方式为主,在有机质、黏土矿物与颗粒表面吸附U(Ⅵ)的基础上,通过硫酸盐还原菌(SRB)还原SO4^2-产生的H2S将U(Ⅵ)被还原成U(Ⅳ),形成铀矿物。The Mengqigu’er uranium deposit in Yili Basin is a typical interlayer oxidation zone type uranium deposit.In order to investigate the origin and formation mechanism of pyrite in ore-bearing sandstone and discuss the process in which microorganisms was involved in uranium mineralization,the authors conducted the detailed analysis of mineralogical characteristics of pyrite and uranium minerals as well as S isotopes of pyrite and C-O isotopes of carbonate cement.The results show that the uranium occurrence of Mengqigu’er uranium deposit is mainly adsorption uranium giving priority to organic adsorption,and uranium mineral mostly is pitchblende closely associated with pyrite and charcoal.The pyrites occurring as euhedral,framboidal,and anhedral forms in the orebearing sandstone of Mengqigu’er uranium deposit are more closely associated with pitchblende and carbonate cement.Theδ34SV-CDT(-68.4‰~22.1‰)of pyrite andδ13CV-PDB(-10.2‰^-7.4‰),δ18OV-PDB(-9.6‰^-5.8‰)of carbonate cement provide direct evidence for bacterial sulfate reduction(BSR)and organic pyrolysis of pyrite.Moreover,the formation mechanism of pyrite of different genesis is also described.Sulfate-reducing bacteria were involved in the uranium mineralization process of Mengqiguer uranium deposit.On the basis of the adsorption U(Ⅵ)of organic matter,clay minerals and particle surface,sulfate ion(SO4^2-)was partially or even totally reduced into H2S by heterotrophic SRB using reactive OM as a source of energy which would reduce U(Ⅵ)into U(Ⅳ)and form uranium and uranium deposits.

关 键 词：地球化学 沥青铀矿 黄铁矿 硫酸盐还原菌(SRB) 铀成矿 蒙其古尔铀矿床 

分 类 号：P619.14[天文地球—矿床学]